Contoured laminated structures, such as instrument panels for automobiles, are well known in the art in which an outwardly presented face of a substantially rigid substrate has laminated thereto a composite sheet having a facing of polyvinyl chloride or other suitable plastics material simulating leather and a backing or core of a foamed plastics material such as foamed polypropylene. Typically, the substrate is a molding formed from an ABS resin or a similar substantially rigid plastics material.
In order to facilitate the lamination of the composite sheet onto the complexly contoured outwardly presented face of the substrate, the substrate is provided with a large number of small perforations in the order of 0.2 to 2.5 mm, and the lamination is effected under the influence of vacuum applied to the rear face of the substrate, in order to draw the composite sheet into intimate face contact with the outwardly presented face of the substrate, and, in order to exhaust air from the interface of the substrate and the composite sheet.
While this technique is successful to an extent, it is encumbered with a major disadvantage that plugging or obstruction of the holes in the substrate can occur, with a consequence that pockets of air remain trapped at the interface of the substrate and the composite sheet, the trapped air interfering with or negating the uninterrupted bonding of the composite sheet to the substrate over the entire area of the interface. The plugging or obstruction of the holes in the substrate occurs as a result of the holes becomming plugged by the adhesive used in the bonding operation, or, by the holes becoming obstructed by the backing of the composite sheet as it is drawn onto the outer face of the substrate under vacuum pressure.
The presence of the trapped pockets of air at the interface poses a particular problem in those instances where the laminated structure is exposed to elevated temperatures, such as can occur within an automobile exposed to direct sunlight, where surface temperatures of the laminated structure may rise to 100.degree. to 110.degree. C.
At such elevated temperatures, the presence of even minute pockets of trapped air at the interface poses a problem, in that expansion of the entrapped air will cause separation of the composite sheet from the substrate in the form of blisters, and an attendant breakdown of the adhesive bond between the composite sheet and the substrate. This problem also can occur during the manufacture of the laminated structure in those instances where the formed structure is subjected to heat in order to speed curing of the bonding adhesive.
As will readily be apparent, the presence of such blisters or imperfections may adversely affect the marketability of the automobile.